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. Author manuscript; available in PMC: 2013 Apr 11.
Published in final edited form as: J Am Chem Soc. 2012 Apr 3;134(14):6088–6091. doi: 10.1021/ja3005094

Figure 1.

Figure 1

Chromophore Structures and Spectral Properties. Chemical structures of 7-azatryptophan (7Aw), 7-methoxycoumarin-4-yl alanine (Mcm), acridon-2-yl alanine (Acd), and a thioamide analog of alanine (A' or Ala') with corresponding wavelengths of maximum absorbance (λmax) and emission (λem). Wavelengths for selective excitation in a protein are listed as λex. Thioamide quenching efficiencies listed as EQ(TA) are for dilute solutions of the fluorophore in 50 mM thioacetamide and as EQ(P2) or as EQ(G2) are those in a short thioamide containing diproline or diglycine peptide, respectively, as described in the text.